Furnace and method of operating the same



June 6, 1933. E. M. FREELAND FURNACE AND METHOD OF OPERATING THE SAME Filed Jan. 24, 1950 Patented June 6, 1933 .UNITED STAT-Es PAT-ENT oFil-rcif;

EDWARD M. FREELAND, or :PITTsrdUIwrH,l PENNSYLVANIA FURNACE AND METHOD or orEnATING THE SAME Application ined January 24,' 1930.v serial No. 423,041.

The present invention relates broadly to the art of heat exchange, and in the embodi-v ment herein illustrated, is directed toward a furnace adapted to heat metals and the like by substantially surrounding themby a gaseous envelope. In this respect'it is particularly adapted to the annealing of sheets, plates and the like, and will hereinafter be delscribed in such connection, although it will be I understood that the utility of the invention is not limited to its particular use or application.

Y In the art of annealing, several lserious problems presentithem'selves. 'Y In the irst (T place, it isneccssary to accurately control the maximum temperature if any uniformity of characteristics in successive batches of metal being 'annealed is tobe obtained It is also necessary to effect the heating in such manner that one portion of the metal being annealed is notrbrought to its full temperature too much in advance of thevremaining portions, inasmuch as this results in holding the yportio'nfirst heated at a soaking temperature while-the remainder of the charge is being brought -up to temperature. This results in articles each of which Vhas diierent characteristics and qualities in d'iierent portions. YThe. present invention provides an improved furnace rstructure andr method of operating the same, whereby not only is heating eected with a material saving in fuel, but with muchgreater uniformity. rIhis results in an improved product at a-less cost'. The figure ofthe drawing shows somewhat diagrammatically one embodiment of my inventionparticularly adapted `for the heating of annealing boxes. In the drawing vthere is shown' a structure such as to be sub- I "40 stantially symmetrical on opposite sides of a verticaly transverse plane Vincluding the line iX- A. 'This' construction provides heating chambers 2 and 3 of similar construction. `The heating chambers are provided with burners 4 and 5, respectively, which are preferably of the natural gas burning type, although other types of fuel may be utilized. The burners are conveniently arranged on Opposite sides of -the heating chambers, and discharge thereinto vthrough ports 6. All

- be tired for 'jByreason of the constructionand 'opera-zA of the ports on a givenside vof a furnace communicate witha 'common mixing and combustion chamber? defined on one. side by thefurnace wall, on the bottomby the fur-- nace bottom, and onthe opposite sideby a .55 bridge wall` 8., eifective for 'distributing the ames and products. of combustion and initially deiiectingl themy upwardy into the upper portions. of the respective heating chambers.

`Each of the heating chambers. is .herein il@ illustrated as having its bottom shapedto receive rolling supports 9 for an annealingfbox -B within which is placed the chargetobe annealed.

Extending through the furnace Abottoms l5 are iuesl() communicating with a conduitv 11, com-mon to the two'heating chambers. `This conduit' is provided withv controllingvalves12 and 12"` adapted to be'closedto cut off com'- municationk between the twov chambers, or opened to establish such communication.

Each heating chamber is also provided with an o-takeflue 13 delivering into apassage 14 in turn communicatingv with a stack S. These ofttake `lues lareY controlled-by valves 7;5 1 Y f In accordance with the present invention, it may be assumed that anannealingbox-is in position in both oftheY heating chambers. At

this time, the burners 4 for the chamber '2v may 80 y ydirectly heating the box'an'd charge in the chamber 2, the-hot products of combustion initially contacting with the top and sides of theannealing box. y"Assuming ,the valve '15 for the chamber'2 -is closed,l the 85 corresponding valve for the chamber 3- open, and the'controlling valves 12 and 12 open these hot gases will pass downwardly around the annealing box in chamber 2, and into'fits flues `10- and conduit 11.; After', passing through this ,conduit, they pass upwardly through the fines 10 of chamber 3 and into such chamber, initially contacting with Y.the bottom of the annealing lbox therein. They then flow upwardly around the sides oflsuch box, then over the top, and iinally escape through the ofltakc flue 13 and passage'lfl of chamber 3 into4 the stack.

tiondescribed, it will be apparent that the 00 heat of Waste gases Which have accomplished their heating duty and Which are ordinarily discharged into the stack, is recovered by passing these gases into a second chamber and abstracting heat therefrom in such chamber. It is further to be noted that in one chamber the hottest gases contact With the top of an annealing box, While in the other chamber, during What may be termed the preheating period, the hottest gases contact with the bottom of the annealing boX therein.

After the charge in the chamber 2 has been brought to the desired temperature and held at such temperature for the necessary length of time, which may be termed the soaking period, the burners 4: may be cut off, and the burners 5 fired. They are effective for delivering the hottest gases to the top of the annealing box in chamber 3, which box has previously been subjected to the greatest heating throughoutits bottom portion. I have found that this accomplishes a very effective method of heating for three reasons:

First: It cuts dovvn the total time required for bringing a charge to the desired temperature.

Second: It. obviates the necessity of first bringing some one part to the required maximum temperature and thereafter holding such part at that temperature While the necessary heating of the remainder of the charge is being accomplished. This has previously been the necessary result of the normal operation of annealing furnaces, and has meant holding one part of a charge at a soaking heat for an unnecessarily long period of time, to the detriment of such part.

Third It insures not only greater uniformity of heating, but also correspondingly greater uniformity of characteristics throughout an entire charge. Y

` To those skilled in the art it Will be apparent that I accomplish What may in effect be termed a reversing operation, the reversal taking place after an initial preheating, and being effective for delivering the hottest gases to that part of the charge previously subjected to the coldest gases, and vice versa.

While the first charge does not obtain the benefit of this reversal, With both preheating and final heating, it is as effectively heated as has heretofore been possible, and more effectively and uniformly heated than Would be the case if the heating gases Were discharged directly into the stack, and not forced to substantially completely envelope the charge. After the initial operation, however, all of the subsequent charges obtain the benefit of this reversal.

In case of necessity, such as represented by the need of repair to one of the furnaces, the

lgases may be directly discharged from one chamber into the stack independently of the Aother chamber. Experience has shown, however, that the life of the furnace is considerably lengthened due to the reversal operation referred to which gives a greater average uniformity of temperature to all parts of the heating chambers, just as it does to the charge.

It will also be apparent that the construction provided enables the furnaces to be operated individually, independently of the offtake flues 13 and passages 14. This may be accomplished, for example, by closing the valves 15 -and opening thevalves 12 and 12', thereby causing the two chambers to discharge their products into the space 16 intermediate the valves 12 and 12, which space in turn is in communication With the flue 17 communicating With a stack S, and suitably controlled by a valve 18. During such periods, the valve 18 Will be open to permit the free disch-arge of gases directly into and through the stack. During such periods, however, as the Waste gases are passing. from one chamber to the other for effecting preheating of the character referred to, the valve 18 Will be closed, thereby compelling the gases to follow the desired path.

The stack S may either be an independent stack, or may be the stack to Which the passages 14 discharge through suitable conduits 19. This stack may be provided With any 'usual type of draft control 20, as customary in the art.

lVhile I have herein described the illustrated furnace as being operated in such manner as to effect a heating of a charge in se-V quence, first by Waste gases from the other chamber, and thereafter by direct firing, the construction is such as to enable these tWo heating operations to occur simultaneously. It may be assumed, for example, that Waste gases are passing from the chamber 2 into the chamber 3, wherein they are initially effective on the bottom of the charge therein.

During this same time, the burners 5 may be operated for simultaneously subjecting the sides and top of such charge to substantially the same temperature conditions. In this manner, the entire outside surface of a given charge or charge container may be simultaneously subjected to such temperature conditions as to insure absolute'uniformity of heating. This is true for the reason that the Waste gases are initially effective on one portion While the products of combustion from the burners delivering to such chamber are initially effective Von the remaining portions. In this manner, a charge can be completely enveloped With heating gases at temperatures such that the desired heating may be obtained. This being true, it is apparent that the heating need not occur in sequence in the manner previously referred to.

The present furnaces, therefore, possess the advantage of being operable either as a series'of individual furnaces, or as a series vfrom such chamber into the of furnaces eHective in tandem, or with the tandem effect in combination with direct firing. This flexibility of operation has not, to my knowledge, been heretofore obtainable With any furnaces heretofore provided.

I am aware that what may be called tandem, series, or double furnaces have been proposed heretofore for heating, reheating, and crucible furnaces, but in cases wit which I am familiar, the operation while it may have contemplated what may be termed alternate firing, has not been effective for accomplishing not only a reversal of the direction of flow of gases, but a reversal also of the heating effect on a furnace charge. p Y

In other words, with structures with which I am familiar, the heating has always, in effect, been in the'same direction, regardless of which furnace was actually being fired.

Furthermore, I am not aware that 'this broad principle of operation has been applied in any case to the annealing of articles en masse as represented by an annealing operation in boxes. For the reasons pointed out, the invention is particularly useful and f desirable when applied to such operation.

This is true not only because of the tre'- mendous saving in fuel, but also on account of the ability to secure the desired temperature conditions throughout an entire charge vgithout detrimental heating of a part there- O l While I have herein illustrated a preferred embodiment of my invention, itfwill bers,

bottom of one chamber wardly through the through the bottom of andthen upwardly the other. chamber. Y

4. In a furnace, a pair of'heating chammeans for firing either of said chambers at will, and passages extending downwardly through the bottom of one chamber below a charge .therein and then upwardly h through the bottom of the other chamber below a charge therein.

5. An annealing pair'of heating chambers, means for supporting an annealing box in each of said chambers for independent removal therefrom, means for firing one chamber lfor initially heating a given portion of a charge therein, means for passing spent gases from such chamber intothe other chamber, said last furnace comprising ay mentioned means being effective for initially heating a different given portion of a charge in the second chamber, said second chamber also having means for firing the same to effect a reversal of the operating cycle, and means for cutting. off communication between the chambers.

In testimony whereof I have hereunto set my hand.

EDWARD M. FREELAND.

be apparent that changes in the particular construction and operation referred to may be made without departing either from the spirit of my invention or the scope of my claims. Y

1. An annealing furnacel comprising a pair of heating chambers, means for supporting an annealing box in each of said chambers for independent removal therefrom, means for firing one chamber for initially heating a given portion of a charge therein, and means for passing spent gases other chamber, said last mentioned means being effective for initially heating a different given portion of a charge in the second chamber, said second chamber also having means for firing the same to effect a reversal of the operating cycle. Y

2. A furnace comprising a pair of heating chambers, means for initially heating the upper and top portion of a charge in one chamber and the lower and bottom portion of a charge in the other chamber, and means for accomplishing a reversal of the heating operation.

3. In a furnace, a pair of heating chambers, means for firing either of said chambers at will, and passages extending down- 

